The invention relates to a shielded connector which can be directly attached to various electric apparatuses such as a power motor.
Conventionally, it is proposed to form a shielded connector which can be directly attached to various electric apparatuses, by integrally molding a metal shell on a connector housing made of a synthetic resin.
An example of a shielded connector A of the integrally molded type will be described with reference to FIG. 6. The shielded connector A comprises a terminal piece 2 which is to be crimped to a terminal of a shielded wire 1, and a connector housing 4 on which a metal shell 3 is integrally molded (see, for example, Japanese Utility Model Unexamined Publication No. Hei. 6-58560).
A connecting member 5 is attached to a braided shield portion 1b which is exposed by peeling off an outer covering layer 1a of the shielded wire 1. A core wire (conductor) 1d which is exposed by peeling off an inner covering layer 1c of the shielded wire 1 is inserted into a bottomed hole 2a formed in one side of the conductive terminal piece 2, and then pressingly fitted by crimping.
The connector housing 4 comprises a cylindrical portion 4a and a flange 4b. The metal shell 3 is embedded between the cylindrical portion and the flange. The terminal piece 2 is inserted into the cylindrical portion 4a.
When the flange 4b is fastened to a metal casing 6 of an electric apparatus by bolts 7, the shield portion 1b is connected with the metal casing 6 through the connecting member 5 and the metal shell 3, thereby establishing a grounding connection.
A bolt 10 passed through an apparatus terminal 8 to which an electric wire 9 is connected is screwed with a thread hole formed in the other side of the terminal piece 2, thereby electrically connecting the apparatus terminal 8 with the terminal piece.
In the thus configured shielded connector A of the integrally molded type, it is difficult to perform a process of improving conformability between the connector housing 4 made of a synthetic resin and the metal shell 3. Therefore, there arises a problem that when a gap is formed between the synthetic resin material and the metal, the shield effect cannot be ensured.
A method in which a synthetic resin material is metal plated may be employed. However, this countermeasure has a problem in that a process of plating a synthetic resin material requires a very high production cost.
FIG. 7 is a longitudinal section view of a shielded connector A, which is adapted to be directly attached to an apparatus and which can be produced at a low cost and attain the shield effect, and FIG. 8 is a perspective view showing main parts of the connector. In the shielded connector A.sub.1, a metal shell 12 is incorporated into a connector housing 11, and the connector housing 11 is directly mounted on (directly attached to) an electrically conductive casing 13 of an electric apparatus such as a motor.
In the connector housing 11, a flange 15 which is to be attached to the casing 13 is formed around one end of a busing 14 which receives an outer cylindrical portion of a counter connector. A bolt insertion hole 16 is formed at the four corners of the flange 15.
A terminal housing portion 17 is disposed in a substantially center area of the flange 15 and in the busing 14. The metal shell 12 is attached to a groove 20 formed in the outer periphery of the terminal housing portion 17. A contact piece 18 bendingly projects from an end portion of the metal shell 12.
In the terminal housing portion 17, a terminal piece 19 is housed on the inner peripheral face which opens at both the ends. Although not shown, the terminal piece 19 and the metal shell 12 are connected with a terminal and a shield member of the counter connector, respectively.
When the flange 15 is fastened to the casing 13 by means of bolts which are passed through the bolt insertion holes 16 and holes 21 of the casing 13, the contact piece 18 is pressingly contacted with the casing 13, thereby establishing an electrical connection therebetween.
The contact piece 18 is inclined so that the tip end portion is closer to the casing 13. When the flange 15 and the casing 13 are fastened together, therefore, the tip end portion of the contact piece 18 accompanied by a resilient force is pressingly contacted with the casing 13. In order to enhance the contact pressure of the contact piece 18, an electrically conductive contact member 22 is inserted between the contact piece 18 and the flange 15.
Reference numeral 23 designates an O-ring, and 24 designates a packing.
Since the contact piece 18 has a shape in which the piece bendingly projects from the end portion of the metal shell 12, the piece is poor in rigidity. When the flange 15 and the casing 13 are fastened together and the tip end portion of the contact piece 18 is kept to be pressingly contacted with the casing 13 for a long time period, the piece is plastically deformed and its elasticity is lost, with the result that the resilient contact force against the casing 13 is gradually lowered. Therefore, the contact stability cannot be expected.
When the casing 13 and the flange 15 are detached from each other for inspection or the like and the connector is then reassembled, the contact piece 18 is contacted with the casing under a state where the original resilient force is lost, so that the reliability of the electrical connection is lowered.
In order to prevent the resilient force of the contact piece 18 from being lowered, the size of the contact piece 18 has been modified, and the material of the metal shell 12 has been changed. However, such countermeasures have problems in that the shielded connector A.sub.1 cannot be made compact so that the desire for a more compact connector can not be met and the production cost is increased.